Normal aging and Alzheimer's disease : hippocampal and episodic memory differences

Alzheimer’s Disease (AD) and normal aging (NA) are characterized by structural brain changes as well as cognitive changes that appear over the lifespan. The hippocampus is an area susceptible to early atrophy in both AD and NA; however the differential causes of atrophy are not entirely clear. Hippocampal volume loss in AD is attributed to neuronal death due to underlying pathology. AD often is diagnosed years after the onset of pathology and subsequent atrophy. NA is a continuation of cognitive decline that does not become dementia. Episodic memory (EM) is processed within the hippocampus and is one of the first systems to show deficits in conjunction with both patterns of aging. This review focuses on hippocampal volume loss and EM decline in NA and AD.Communication Sciences and Disorder

Comparison of prefrontal atrophy and episodic memory performance in dysexecutive Alzheimer’s disease and behavioural-variant frontotemporal dementia

Alzheimer’s disease (AD) sometimes presents with prominent executive dysfunction and associated prefrontal cortex atrophy. The impact of such executive deficits on episodic memory performance as well as their neural correlates in AD, however, remains unclear. The aim of the current study was to investigate episodic memory and brain atrophy in AD patients with relatively spared executive functioning (SEF-AD; n = 12) and AD patients with relatively impaired executive functioning (IEF-AD; n = 23). We also compared the AD subgroups with a group of behavioral-variant frontotemporal dementia patients (bvFTD; n = 22), who typically exhibit significant executive deficits, and age-matched healthy controls (n = 38). On cognitive testing, the three patient groups showed comparable memory profiles on standard episodic memory tests, with significant impairment relative to controls. Voxel-based morphometry analyses revealed extensive prefrontal and medial temporal lobe atrophy in IEF-AD and bvFTD, whereas this was limited to the middle frontal gyrus and hippocampus in SEF-AD. Moreover, the additional prefrontal atrophy in IEF-AD and bvFTD correlated with memory performance, whereas this was not the case for SEF-AD. These findings indicate that IEF-AD patients show prefrontal atrophy in regions similar to bvFTD, and suggest that this contributes to episodic memory performance. This has implications for the differential diagnosis of bvFTD and subtypes of AD

Social capabilities in Alzheimer’s patients

Patients with stage-I (very mild and mild) Alzheimer’s disease were asked to participate in a Dictator Game, a type of game in which a subject has to decide how to allocate a certain amount of money between himself and another person. The game enables the experimenter to examine the influence of social norms and social preferences on the decision-making process. When the results of treatments involving Alzheimer’s disease patients were compared with those of identical treatments involving patients with mild cognitive impairment or healthy control subjects, with similar ages and social backgrounds, no statistically significant difference was found. This finding suggests that stage-I Alzheimer’s disease patients may be as capable of making decisions involving social norms and preferences as other individuals of their age. Whatever brain structures are affected by the disease, they do not appear to influence, at this early stage, the neural basis for cooperation-enhancing social interactions.Alzheimer patients, social behavior, dictator games

Second language performances in elderly bilinguals and individuals with dementia: The role of L2 immersion

With the population aging and an increase in the number of senior immigrant citizens in modern societies, public health systems will be increasingly burdened with the need to deal with the care and treatment of bi- or multilingual individuals with cognitive decline and dementia. This raises complex questions such as which language is better preserved in these elderly individuals, particularly for those facing dementias. The main aim of the present investigation was to study in two groups of immigrant populations whether the first language (L1) or the second language (L2) are better preserved. For this purpose, we assessed by means of cognitive and neurolinguistics testing 20 late-bilingual individuals with neurodegenerative dementia of the Alzheimer and mixed type, and compared their results to a matched control group consisting of 19 subjects. Our results suggest that L1 is not better preserved in individuals with dementia. We report a parallel decline of second language across groups, regardless of the presence of dementia, as well as a significant correlation between language immersion and L2 relative performances (r = 0.379, p = 0.03). Moreover our data suggest that individual with dementia may have a relative sparing of syntactic L2 comprehension. These results suggest that these elderly individuals who have lived in a host country for many years, such as the subjects here investigated, may preserve similarly their L2 as much as their L1, irrespectively of the presence or absence of neurodegenerative disease, and even preserve some features of L2 processes in dementia. These results emphasize the role of immersion in language preservation

Comparative Memory/Behavioral Symptoms of Alzheimer\u27s disease: EOAD vs. LOAD

Alzheimer\u27s disease (AD) is a fatal disorder with no apparent cure. Early-onset AD (EOAD) occurs in individuals before the age of 65, and late-onset AD (LOAD) occurs in individuals age 65 and older. Past studies have proven that AD is fatal among Americans age 65 and older. The disease is characterized by impairments in memory and executive function as well as other cognitive and behavioral problems. The research questions addressed by this sequential, mixed-method study compared EOAD and LOAD by exploring common behavioral/cognitive symptoms and stage levels of AD. Research participants were recruited from the Alzheimer\u27s Association who were members of caregiver support groups and cared for an individual with AD. The qualitative component of this study consisted of a qualitative interview given to caregivers (N = 6), which was audio-recorded and transcribed verbatim using the 6-phase thematic analysis. Sequentially, the quantitative component of this study consisted of the BEHAVE-AD and Short IQCODE instruments, which were filled out and completed by caregivers (N = 20) on behalf of patients with probable AD. These data were analyzed using 1-way ANOVA, with the alpha set at 0.05. Integration of qualitative and quantitative results indicated no differences in cognitive or behavioral symptoms of either EOAD or LOAD care recipients. These findings have implications for positive social change by continually involving caregiver participants in future studies. Doing so can ensure that care recipients, whether they have been diagnosed at EOAD or LOAD, have a voice

Preservation of episodic memory in semantic dementia:The importance of regions beyond the medial temporal lobes

Episodic memory impairment represents one of the hallmark clinical features of patients with Alzheimer's disease (AD) attributable to the degeneration of medial temporal and parietal regions of the brain. In contrast, a somewhat paradoxical profile of relatively intact episodic memory, particularly for non-verbal material, is observed in semantic dementia (SD), despite marked atrophy of the hippocampus. This retrospective study investigated the neural substrates of episodic memory retrieval in 20 patients with a diagnosis of SD and 21 disease-matched cases of AD and compared their performance to that of 35 age- and education-matched healthy older Controls. Participants completed the Rey Complex Figure and the memory subscale of the Addenbrooke's Cognitive Examination-Revised as indices of visual and verbal episodic recall, respectively. Relative to Controls, AD patients showed compromised memory performance on both visual and verbal memory tasks. In contrast, memory deficits in SD were modality-specific occurring exclusively on the verbal task. Controlling for semantic processing ameliorated these deficits in SD, while memory impairments persisted in AD. Voxel-based morphometry analyses revealed significant overlap in the neural correlates of verbal episodic memory in AD and SD with predominantly anteromedial regions, including the bilateral hippocampus, strongly implicated. Controlling for semantic processing negated this effect in SD, however, a distributed network of frontal, medial temporal, and parietal regions was implicated in AD. Our study corroborates the view that episodic memory deficits in SD arise very largely as a consequence of the conceptual loading of traditional tasks. We propose that the functional integrity of frontal and parietal regions enables new learning to occur in SD in the face of significant hippocampal and anteromedial temporal lobe pathology, underscoring the inherent complexity of the episodic memory circuitry

The effect of memory test instructions on shifts in response bias in individuals with and without Alzheimer's disease

Patients with dementia due to Alzheimer's disease (AD) tend to exhibit impairments in in their episodic memory. In yes-no tests of recognition memory, patients with AD often display liberal response bias, a stronger tendency to recognize unstudied items as already-studied "old" items. Such tendency is believed to be related to false memory, which can decrease the quality of life in many AD patients. In this study, we analyzed the effect of different instructional manipulations within yes-no recognition memory task on response bias. Younger healthy adults, older healthy adults and one AD patient were evaluated for recognition memory performance and response bias in three different conditions of instructional manipulation. In each session separated by a week-long interval, participants were shown 120 words to study and 240 words, half of which were studied items, to be tested for recognition memory. Instructional manipulation was added in the testing phase of each condition. In one session, the participants were asked if the words were old, studied items; in another session, they were asked if the words were new, unstudied items; finally in the third session, participants were asked to identify if the words were either old or new. Our findings corroborated previous studies by observing liberal response bias in AD and moderately conservative response bias in health adults. We found that the instructional manipulations did not have a significant effect on response bias in either control group while the effect in the AD patient was inconclusive

Diagnostic and prognostic role of semantic processing in preclinical Alzheimer's disease

Relatively spared during most of the timeline of normal aging, semantic memory shows a subtle yet measurable decline even during the pre-clinical stage of Alzheimer's disease. This decline is thought to reflect early neurofibrillary changes and impairment is detectable using tests of language relying on lexical-semantic abilities. A promising approach is the characterization of semantic parameters such as typicality and age of acquisition of words, and propositional density from verbal output. Seminal research like the Nun Study or the analysis of the linguistic decline of famous writers and politicians later diagnosed with Alzheimer's disease supports the early diagnostic value of semantic processing and semantic memory. Moreover, measures of these skills may play an important role for the prognosis of patients with mild cognitive impairment